1. Field of the Invention
The present invention relates to a linear compressor, and more particularly to an improved linear compressor employing an axial flow valve system, wherein a refrigerant suction guide hole is axially formed through an interior of a piston which is slidingly provided in a cylinder and supported by a spring.
2. Description of the Conventional Art
In order to solve disadvantages of a linear compressor adopting a crank shaft, a magnet and coil assembly replacing the crank shaft has been employed for a shuttle movement of a piston, thereby decreasing compressor parts number and production cost, and enhancing productivity.
As shown in FIG. 1, such a conventional linear compressor includes a cylinder 2 provided in a hermetic vessel 1 which has a predetermined shape.
In the cylinder 2, coil assemblies 3, 3' are assembled into a single body.
A piston spring 4 is fixed to a lower portion of the cylinder 2 thus to be connected to a lower circumferential portion of the cylinder 2, and a plurality of mounting springs 7 provided between the piston spring 4 and an inner bottom portion of the hermetic vessel 1 serve to elastically support the piston spring 4.
A piston 5 is fixed to a center portion of an upper surface of the piston spring 4 so as to carry out a linear shuttle movement in the cylinder 2.
A magnet 6 is fixedly attached along an outer periphery of the piston 5, and a valve assembly 8 is fixed to a side portion of an upper surface of the cylinder 2. A suction side muffler 9 and an exhaustion side muffler 10 are respectively installed adjacent to each side of the valve assembly 8.
The thusly constituted conventional linear compressor repeatedly carries out sequential operations of suction, compression and exhaustion of refrigerant gas in accordance with a repeated linear shuttle movement of the piston 5.
With regard to operation of the conventional linear compressor, because an assured opening/closing operation of a suction valve and an exhaust valve which control the flow of refrigerant gas serves as a significant factor in improving compressor efficiency, there is widely known a linear compressor employing an axial flow valve system in order for the flow direction of refrigerant gas to be directed identically to that of piston movement.
An inertia-applied valve apparatus applicable to a reciprocal movement compressor serving as an example of the axial flow valve system will now be described.
As shown in FIG. 2 illustrating the inertia-applied valve apparatus, a recess 21a is formed in and along an inner peripheral portion of a cylinder 21, and a plurality of refrigerant suction holes 21b are respectively formed through a portion of the bottom surface of the recess 21a so as to communicate with an exterior of the cylinder 21.
A chamfer opening 22a is formed outside each chamfer of an end of the piston 22 which is received in the cylinder 21 so as to communicated with the recess 21a.
A suction valve 23 is caulked around a center portion of a top surface of the piston 22 by a piston pin 24.
To an end of the cylinder 21 there is connected a head cover 25 which communicates with an interior of the cylinder 21.
A spring 27 is connected to an inner side portion of the head cover 25, and an exhaust valve 26 is connected to an end portion of the spring 27 and elastically supported by the spring 27.
Through a predetermined portion of the head cover 25 there is formed a refrigerant gas exhaust hole 25a to communicate with an exterior of the head cover 25.
When refrigerant gas compressed in a compression space C of the cylinder 21 pushes the exhaust valve 26 against the elasticity of the spring 27, the compressed refrigerant gas exhausts through the refrigerant exhaust hole 25a at the head cover 25.
In the thusly constituted conventional linear compressor employing an axial flow valve system, when refrigerant gas is sucked into the cylinder 21 via the refrigerant suction hole 21b and the recess 22a at the cylinder 21, the suction valve 23 becomes spaced from the piston 22 in accordance with a pressure difference between respective side end portions of the suction valve 23 for thereby facilitating an intake stroke of the piston 22 as shown in FIG. 2, so that when the suction valve 23 is moved toward a direction further away from the exhaust valve 26, the refrigerant is sucked into the compression space C through a gap between the suction valve 23 and the piston 22.
The refrigerant sucked into the compression space C is compressed during a compression stroke of the piston 22, and accordingly the exhaust valve 26 is moved toward a direction against the elasticity of the spring 27, whereby the refrigerant is exhausted through the refrigerant exhaust hole 25a formed at the head cover 25.
After the compression stroke of the piston 22, the piston 22 causes the suction valve 23 moved toward a front direction of the piston 22 to move in a direction facing against the exhaust valve 26 for thereby repeating the above-described suction operation. At this time, the suction valve 26 returns to an initial state in response to the restoring force of the spring 27.
However, the linear compressor without employing an axial flow valve system as shown in FIG. 1 is provided with the muffler 9 installed at an entrance of a refrigerant path adjacent to the valve assembly 8, and noise occurring around the entrance of the refrigerant path can be efficiently muffled. Meanwhile, despite a great need for reducing suction noise resulting from the suction side opening of the refrigerant path, because there exists a structural disadvantage in which the flow direction of refrigerant is identical to the movement direction of the piston, the linear compressor employing the axial flow valve system as shown in FIG. 1 which is widely accepted due to its assured valve opening/closing operation is not appropriate to installing an suction side muffler as in the linear compressor without employing an axial flow valve system as shown in FIG. 1 and further it is not equipped with an extra noise reduction apparatus therein, thereby presenting a serious noise problem.
With reference to Korean Patent Application No. 25666 filed by the present patent applicant in 1995, in order to solve the above-described problems, a linear compressor as shown in FIG. 3 is provided with a piston 32 slidingly combined in the cylinder 31, wherein the piston 32 is separately comprised of an outer piston 33 combined along an inner periphery of the cylinder 31, a rod post 34 provided within the outer piston 33, and a piston rod 35 connected through the rod post 34.
In the linear compressor as shown in FIG. 3, between the piston rod 35 and the rod post 34 there is formed a first silencer 36 which communicates with an entrance portion of refrigerant gas path, and between the rod post 34 and the outer piston 33 there is formed a second silencer 37 which communicates with the first silencer 36.
At apredetermined portion of the rod post 34 there is formed a hole 34a in order for the first silencer 36 and the second silencer 37 to communicate with each other.
In each side portion of an end surface of the piston 32 there is formed a piston hole 32a, and a suction valve 41 is caulked in a center portion of the piston 32 by a piston pin 42.
In a housing recess 43a covered by a head cover 43 which is fixed to each side portion of the cylinder 31 there are insertingly provided a first exhaust valve 44, a second exhaust valve 45, a stopper 46 and a spring 47.
Between the hermetic vessel 55 and cylinder 31 there is provided a hermetic spring holder 51 each end portion of which is connected to a predetermined portion of the cylinder 31 and which has a shape surrounding the cylinder 31.
At this time, an entrance portion of the hermetic spring holder 51 positioned along a direction toward which the refrigerant gas is sucked is connected to the cap 52 having a suction tube 54 formed through a portion thereof, wherein the refrigerant suction tube 54 serves to suck the refrigerant gas therethrough.
As a result, there is formed a third silencer 53 inside of the cap 52, for thereby doubling noise reduction efficiency.
Meanwhile, a dominant equation for a mechanism of the thusly composed linear compressor is as follows: EQU X=1/m {.alpha.I-A.sub.p (P.sub.w -P.sub.b)-(X-KX)}
wherein,
m=moving mass including a piston; PA1 A.sub.p area of front side of the piston; PA1 P.sub.w =pressure of compression portion; PA1 P.sub.b =pressure of rear portion of the piston; PA1 K=stiffness of a mechanical spring; and PA1 C=damping coefficient.
Here, spring constant K required to operate the linear compressor has come into existence, and in order to satisfy spring constant K, there is employed a plate spring 28 as shown in FIG. 4.
The plate spring 28 is assembled with the piston rod 35.
Reference numeral 48 denotes a refrigerant exhaust tube, reference numeral 56 denotes an external refrigerant suction tube, and reference numeral 57 denotes an external refrigerant exhaust tube. Here, the refrigerant exhaust tube 48 and the external refrigerant exhaust tube 57 communicate with each other, though not illustrated in the drawing, with reference to FIG. 3, the operation of noise reduction apparatus of the conventional linear compressor will now be described.
When the linear compressor shown in FIG. 3 starts operation, refrigerant gas is sucked through the external refrigerant suction tube 56 at the hermetic vessel 55, and the sucked refrigerant gas flows through the internal refrigerant suction tube 54 formed through the cap 52 to the third silencer 53 attain a primary noise reduction.
Then, the refrigerant gas flows along the arrow direction from a rear side of the cylinder 31 and through the refrigerant gas path into the cylinder 31. At this time, because the first silencer 36 is formed between the piston rod 35 and the rod post 34, when the refrigerant gas passes through the first silencer 36, there is obtained a secondary noise reduction effect.
A tertiary noise reduction effect is obtained when the refrigerant gas passes through the second silencer 37 formed between the rod post 34 and the piston 33 after passing through the hole 34a formed through the rod post 34.
Next, the refrigerant gas that has flowed into the compression space C in the cylinder 31 after passing through the piston hole 32a of the piston 32 and the suction valve 42, respectively, moves toward the first exhaust valve 44 in order for the piston 32 to carry out a compression stroke thereof. Then, passing through the first and second exhaust valves 44, 45, the refrigerant gas is externally exhausted through the refrigerant exhaust tube 48 of the head cover 43.
At this time, the stopper 46 serves to prevent the second exhaust valve 45 from moving excessively.
However, in the linear compressor shown in FIG. 3, the refrigerant gas which passed through the external refrigerant suction tube 56 is flowed through the internal refrigerant suction tube 54, which is formed at the cap 52 as a tiny hole, into the inner space of the linear compressor, and further in order for the refrigerant gas to flow into the cylinder 31, the refrigerant gas should pass through the piston 32 which has a complicated structure.
That is, conventionally, the externally sucked refrigerant gas is heated while passing through the internal refrigerant path of the piston 32 remains at a high temperature, whereby volume of the refrigerant gas becomes increases, and a cooling efficiency of the refrigerant gas deteriorates. In addition, an increased refrigerant path damage has been taken place resulting from the narrow internal refrigerant path in the piston.
Further, the conventional linear compressor has a disadvantage in that the outer piston 33, the rod post 34 and the piston rod 35 which are formed into the piston assembly need be connected to each other using a heat compression method.